The important issue from this AV report:
According to information The Aviation Herald received on March 4th 2017 the CL-604 passed 1000 feet below an Airbus A380-800 while enroute over the Arabic Sea, when a short time later (1-2 minutes) the aircraft encountered wake turbulence sending the aircraft in uncontrolled roll turning the aircraft around at least 3 times (possibly even 5 times)
So the aircraft were flying apart and 1 - 2 minutes later the Challenger was rolled by the wake. That must be 20 - 30 miles behind the 380 and a thousand feet below it the wake was strong enough to roll a bizjet. For those offsetting a couple of miles to avoid wake that may well not be enough with these kinds of figures.
It may also explain the occasional CAT with pax and flight attendants hurt when the flight was otherwise smooth who would suspect an aircraft 30+ miles away?